If a 30-foot tree casts a 12-foot shadow, find the length of the shadow cast by a 28-foot tree.

Given the information, we can create 2 ratios: tree height over shadow length

This gives us:
30/12 = 28/x

We then need to solve for x by cross multiplying:
30x = 336

Then we can divide 336 by 30:

As a reduced fraction:
x = 56/5 ft

As a decimal:
x = 11.2 ft